The present invention relates to a new and improved construction of carburetor for an Otto cycle engine or Otto carburetor engine, which carburetor is of the type comprising a mixing compartment through which flows a suction air current regulated by a regulating valve, and within the mixing compartment there is prepared the fuel which is infed in a dosed manner by nozzles for forming the fuel-air mixture for the Otto cycle engine.
One of the primary efforts which is being made at the present time is to reduce the proportion of noxious constituents contained in the exhaust gases of Otto cycle engines. Recently a great deal of effort has been expended to solve this problem and, accordingly, there have become known in this particular field of technology many different processes and apparatuses which are intended to produce exhaust gases having a low ccontent of noxious or harmful substances, in fact even totally free of such noxious substances. It has been found that even when using a conventional carburetor operating at constant conditions, it is possible to obtain exhaust gases which at least are almost free of noxious substances, if the carburetor is adjusted very accurately. The high proportion of noxious substanes in the exhaust gases of an Otto cycle engine therefore is apparently primarily attributable to improper dosage of the fuel, i.e. it is not so much the engine itself which is responsible for the formation of the noxious substances, primarily rather the carburetor and the injection device, and even in a conventional engine without any changes carried out thereat, considerably better results can be expected in this regard if the fuel is exactly dosed as a s function of the operating conditions.
For the combustion of 1 kilogram fuel in an Otto cycle engine, depending upon the operating conditions (idling, partial load, full load) there are required approximately 11 to 18 kilograms of air. Preparation of the fuel-air mixture occurs in the mixing compartment where there is distrubuted as uniformly as possible a predetermined quantity of fuel into a sucked-up quantity of air. The addition of fuel is generally requlated primarily as a function of the negative pressure generated in the suction conduit. The dependency of the sucked-up quantity of air upon the negative pressure for conventional carburetors can be expressed by a rather complicated equation. Generally considered there can be used for this purpose a second power function, and the quantity of fuel more or less linearly increases with the quantity of air. Thus, for such type carburetor a considerable expenditure is required in order to realize an exact dosing of the fuel. Hence, it is hardly possible to solve the prevailing porblem by means of a pressure-dependent regulated dosage of the fuel. Furthermore, a number of other constructions of carburetors have become known or proposed, which however likewise are associated with the drawback that they are inaccurate in operation and/or expensive.
Essential for the operation of an Otto cycle engine is, however, not only the dosage of the fuel but also the preparation of the fuel-air mixture. For judging the quality of the obtained fuel-air mixture two criteria are sufficient in practice: particle size and condensation of fuel at the walls of the carburetor. The fuel particles or droplets should possess a diameter of about 10to 20 .mu. m and the walls of the carburetor should be dry in any case. If there is present too good "carburization" of the fuel with a particle size below 10 .mu. m then the efficiency of the engine drops, and with poor carburization with fuel droplet or particle diameters exceeding 20 .mu. m and condensation of fuel at the carburetor walls the combustion becomes faulty, such incomplete combustion of the fuel being considered the cause for the noxious CH-compounds (hydrocarbon compounds) which are present at the exhaust gases. In the case of an ideal prepared fuel-air mixture it thus would be necessary to uniformly distribute in the sucked-up air small fuel droplets or particles of the same predetermined size and which must be at rest relative to the flowing air. Such ideal fuel-air mixture basically cannot be produced with an injection carburetor, yet in the interest of environmental controls it is necessary that there be obtained as close as possible approximation of such ideal conditions.